Supply chain operations require real-time information regarding location of freight and transportation equipment. Global positioning systems (GPS) may assist in identifying an approximate position in an open environment yet typically are not available in an enclosed environment, like inside a building. Warehousing operations require this real-time location information, however provide a less than ideal condition for many forms of location identification. GPS signals typically do not propagate well into building structures. In addition, GPS location data has an inherent inaccuracy of as much as several meters that renders this type of location data of little or no assistance in an environment where this level of inaccuracy may provide an inability to identify one aisle of the warehouse from either immediately adjacent aisles.
Radio Frequency Transmitter Devices (RFIDs) are useful for identifying when an RFID tag attached to the mobile device passes designated locations wherein an RFID reader is positioned, however do not help with real-time tracking. Particularly, RFID-based systems cannot identify a precise location of an RFID tag. These systems only provide information that the RFID tag is within a transmit/receive area of the RFID reader.
Other Real Time Locating Systems (RTLSs) exist that use a triangulation technique to identify a location of the mobile device. In operation, transmitter/receivers in a form of network access points are positioned throughout an area wherein the mobile device travels. The mobile device is arranged to transmit a beacon signal that is receivable by the access points. A time difference of arrival of the beacon signal at the access points is utilized to determine a distance of the mobile device from the access points (typically three or more). The distance from the access points and triangulation techniques are utilized to identify the location of the mobile device. However, these systems are unreliable because an accurate location calculation requires communication with multiple access points. In a warehouse environment, oftentimes a sufficient number of access points may not be receivable due to null points and geometry obstructions. Placement of a sufficient number of additional access points may be cost prohibitive. As a result, the mobile device may be disconnected from the network for periods of time where real-time location data is unavailable.
It is an object of the present system to overcome disadvantages and/or make improvements in the prior art.